allow produce and consume to pass values in both directions. closes #…

…4775

base/task.jl

@@ -49,13 +49,13 @@ function produce(v)
  # make a task waiting for us runnable again
  notify1(q)
  end
- yieldto(ct.last, v)
+ r = yieldto(ct.last, v)
  ct.parent = ct.last # always exit to last consumer
- nothing
+ r
 end
 produce(v...) = produce(v)
 
-function consume(P::Task)
+function consume(P::Task, values...)
  while !(P.runnable || P.done)
  if P.consumers === nothing
  P.consumers = Condition()
@@ -65,7 +65,7 @@ function consume(P::Task)
  ct = current_task()
  prev = ct.last
  ct.runnable = false
- v = yieldto(P)
+ v = yieldto(P, values...)
  ct.last = prev
  ct.runnable = true
  if P.done